Rotary blow molding machine with movable clamp assemblies and method

ABSTRACT

A continuous blow molding machine includes a mechanism for shifting molds upstream after closing to reduce between-mold flash.

FIELD OF THE INVENTION

The invention relates to continuous rotary blow molding machines withmold clamps and to methods for blow molding articles.

DESCRIPTION OF THE PRIOR ART

Conventional continuous rotary blow molding machines extrude one or morecontinuous parisons for capture in cavities in adjacent molds for blowmolding. Mold flash extends between mold cavities in adjacent molds andtypically includes a blow dome. The flash must be cut away from thebases and necks of the bottles. The cut at the neck must be machined toform a flat surface perpendicular to the neck axis for making a sealwith an applied closure. The flash is waste and must be discarded. Theflash trimming and machining operations increase the cost of blow moldedbottles.

In continuous rotary blow molding machines, one flow head continuouslyextrudes a parison for capture in each mold cavity in each mold.Parisons must be extruded at the circumferential speed of each moldcavity. The cavities are spaced radially and have differentcircumferential speeds. As a result, a separate parison controller isrequired for each flow head in order to extrude the parison at therequired speed and to vary the thicknesses of the parison to obtain adesired container weight.

SUMMARY OF THE INVENTION

The invention is an improved rotary blow molding machine in which moldclamp assemblies including molds are movably mounted on a continuouslyrotating frame. The blow molding machine includes an assembly drive forshifting the mold clamp assemblies between upstream and downstreampositions on the frame as the frame continuously rotates downstreamduring blow molding. Flash is reduced. Blow pins may be used to form thenecks of bottles. Parison extrusion equipment is simplified.

In the improved machine each open mold is in a downstream position onthe rotating frame when the mold is rotated over one or more parisons.After the rotating open mold closes to capture the parison or parisons,the assembly drive shifts the mold upstream from the downstream positionto slow rotation of the mold and maintain the mold cavity or cavities inalignment with and moving above the flow heads at the same speed and inthe same direction as the parisons are extruded. Upstream shifting ofthe closed mold continues during closing of the next mold on theparisons. Each mold holds the extruded parison or parisons in alignmentduring closing of the next mold.

The next upstream mold is adjacent to the previously closed mold when itcloses on the parison or parisons. A parison knife on the upstream endof the previously closed mold then severs the parison or parisonsbetween the molds. The next upstream mold then moves upstream and awayfrom the previously closed mold to provide a gap between the molds.

Each mold clamp assembly includes a blow pin unit mounted on the mold.The blow pin unit is moveable from a retracted position away from themold to a blow position on the downstream side of the closed mold and ina gap between molds to position a blow pin adjacent each open end of aparison segment held in a cavity in the mold. The blow pin unit issecured on its mold to permit extension of the blow pins into the openends of the cavities to compact and firm neck finishes for the bottlesand to flow compressed gas into the cavities to blow captured parisonsegments against the molds for forming bottles. The blow pin unitsremain mounted on molds with pins extended during blow molding andcooling of the blown bottles.

After the plastic in blow molded bottles has cooled and set, the blowpins are withdrawn and the blow units are retracted, the mold halves areopened and the bottle or bottles are ejected. The mold is then shiftedon the frame from the upstream position back to the downstream position.The open mold in the downstream position is then moved over the flowhead or flow heads and parisons to initiate a new cycle of operation.

In improved machines according to the invention using multi-cavitymolds, each parison is identical and is extruded at the same rate withthe same wall thickness profile using a single extruder for each plasticresin in the parison and a single flow controller for all of the flowheads. The parisons are all extruded upwardly at the same speed which isless than the circumferential speed of the mold to reduce between bottleflash.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a mold clamp assembly mounted on the frame of avertical rotary blow molding machine;

FIG. 2 is a side view of a vertical rotary blow molding machineillustrating mold clamp assemblies at the top and bottom of the machinewith other assemblies and components broken away;

FIGS. 3 and 4 are views of the machine in FIG. 2 taken generally alonglines 3-3 and 4-4;

FIG. 5A is a view taken generally along line 5A-5A of FIG. 4;

FIG. 5B is a view similar to FIG. 5A but with the mold closed and blowpin unit shifted over the mold; and

FIG. 6 is an enlargement of a portion of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1 to 6 illustrate a rotary blow molding machine 100 including arotary frame 102 having a horizontal main shaft 104 with ends journaledin bearings mounted on shaft supports 106 and 108. Three circularmounting plates 110, 112 and 114 are mounted on and rotate with shaft104. Sixteen mold clamp assemblies 116 are mounted on the plates atcircumferential locations spaced around the frame.

The rotary frame 102 and assemblies 116 are continually rotated aroundthe axis of the main shaft 104 by a conventional drive 103, which may bean electric motor in the direction of arrow 232 shown in FIGS. 3 and 4.Rotation of frame 102 continuously moves the mold clamp assemblies 116downstream past extrusion, blow molding, cooling and ejection stationsspaced around the machine.

Shaft supports 106 and 108 form parts of a stationary main frame 109.Partial circumferential upstream shift or retard cam 118 is mounted onsupport 108 facing plate 110. Partial circumferential mold open and moldclose or actuation cam 120 is mounted on shaft support 106. Partialcircumferential downstream shift or advance cam 122 is mounted onsupport 106. The cams 118, 120 and 122 include grooves with angledsurfaces for engaging cam follower rollers carried by mold clampassemblies 116.

As illustrated in FIG. 1, each mold clamp assembly 116 includes a base124 extending parallel to the axis of main shaft 104. Mold platens 126and 128 are mounted on tension rods 130. Rods 130 are mounted on base124 by supports 132 and 134 to permit movement of the platens along therods toward and away from each other during opening and closing of moldhalves 136 and 138 mounted on the platens. Mold halves 136 and 138 eachhave two cavities 140 and form a two cavity mold 142 when closed. Rods130 are parallel to the main shaft axis and extend freely throughpassages 144, 146 in supports 132, 134. Transverse end plates 148, 150are mounted on the opposite ends of base 124.

A pair of spaced plates 152 are mounted on plate 148 and the adjacentend of base 124. Only one plate 152 is illustrated. Pin 154 is mountedin openings in the plates 152 and extends between the plates. The pin154 is located to one side of mold halves 136 and 138. The adjacent endsof tension rods 130 are secured to pin 154. Pivot arm 156 is rotatablymounted on pin 154 between tension rods 130. The outer end 158 of arm156 away from the mold halves extends through an opening in plate 148and is connected to a slide car 160 mounted on plate 148 by links 162.Slide car 160 is mounted on the side of plate 148 away from mold 142 byslide 164 to permit movement of the car back and forth in the directionof arrow 166 shown in FIG. 1. Car 160 carries a cam follower roller 168which extends into the slot in mold open and close cam 120. Rotation ofeach assembly 116 with the main shaft 104 moves each follower 168 alongthe groove in cam 120 to shift car 160 radially inwardly and outwardlyon plate 148 and rotate arm 156 between the mold open position shown inthe bottom of FIG. 2 and the mold close position shown in FIG. 1 and inthe top of FIG. 2.

Mold shift member 170 is located between mold platen 126 and plate 148.The upper end 172 of member 170 is bolted directly to mold platen 126.Movement of the member 170 toward plate 148 moves the mold halves fromthe closed position to the open position. The lower end 174 of shiftmember 170 is located below the mold platens and mold halves. Pivot link176 is rotatably connected to the inner end 178 of arm 156 and to moldshift member 170. The pivot connection between link 176 and member 170is located halfway between the upper end 172 and lower end 174 of shiftmember 170 to balance forces.

Shift rod 180 is located under base 124, extends parallel to the axis ofmain shaft 104 and is moveable along the base. One end of the shift rod180 is connected to the lower end 174 of shift member 170. Pivot link176 and adjacent end 178 of arm 156 form a two link extendable andretractable drive 182 for opening and closing mold halves 136 and 138.

Cross pin 184 is mounted on the ends of tension rods 130 extending pastmold half 136 and rotatably supports pivot arm 186. The lower end 188 ofarm 186 is connected to the adjacent end of shift rod 180 by pivot link190. The upper end 192 of arm 186 is connected to mold clamp rod 194 bypivot link 196. Clamp rod 194 extends freely through support 132 and isconnected to platen 128 through dished washer spring pack 198. The shiftrod 180, arm 186, rods 130 and 194 and member 170 are part of a moldshift mechanism 200 for opening and closing mold half 136 in response tomovement of shift member 170. The mechanism 200 is connected to theextendable and retractable drive 182 to move mold half 136 through moldshift member 170, rod 180, arm 186 and rod 194.

As shown in FIG. 1, plates 148 and 150 include lower ends 204 and 206extending below base 124. Pivot support rod 208 extends between ends 204and 206 parallel to base 124 and to the axis of main shaft 104. Rod 208extends through pivot bearings 207 mounted on plates 110, 112 and 114 tomount the mold clamp assembly on the rotary frame 102 and permitrotation of the assembly 116 around the rod as follower rollers 210 and212 move along grooves in shift cams 118 and 122.

Cam follower roller 210 is mounted on plate end 204, below rod 208.Roller 210 engages the groove in mold shift or advance cam 122. Camfollower roller 212 is mounted on plate 150 above pivot support rod 208and engages the groove in shift cam 118. During rotation of frame 102,the angled surfaces in cams 118 and 122 pivot the assemblies 116 backand forth about rods 208 to shift the molds upstream and downstreamrelative to the rotating frame 102.

Each mold clamp assembly 116 includes a blow pin unit 214 suitablymounted on the downstream facing side 216 of mold half 136. A pressurecylinder drive 137 on mold half 136 moves the unit between a retractedposition shown in FIG. 5A and a blow position shown in FIG. 5B. Eachmold half 136, 138 includes a blow unit mounting plate 218 which extendsover one edge of a blow pin unit 214 and holds the blow pin unit againstthe downstream side of the closed mold with blow pins 220 located aboveneck cavities 222 in the closed mold. The blow pin unit includespressure cylinders 224 for extending the blow pins into the cavities.The blow pins also include conventional blow passages for flowingcompressed gas into parison segments captured in the cavities duringblow molding. FIG. 6 illustrates a first blow pin unit 214 a in theretracted position and a second blow pin unit 214 b in a work positionover a mold 142. When in the work position, the blow pin unit 214 b islocated in gap 226 between adjacent mold clamp assemblies 116.

Molds 142 each include two cavities 140. Vertical rotary blow moldingmachine 100 includes two flow heads 228 located on the main frame of themachine in alignment with the closing faces of molds 142 and below theposition of the molds when the molds are fully closed by drive 182. SeeFIGS. 3 and 4. Each flow head 228 extrudes a like parison 230 verticallyupwardly at the same extrusion rate or speed for capture in one cavityof each mold 142 as the molds are moved vertically above the flow headsand closed. Parisons 230 are identical and are each extruded verticallyupwardly at a speed equal to the upward speed of the mold closing on theparisons. The closed mold moves vertically upwardly above the flow headsto align the captured parisons extending between the flow heads and themold for capture by the next or upstream open mold which is rotated pastthe flow heads and closed on the aligned parisons. Because the parisonsare identical and are extruded at the same speed, a single controller233 is required for the two flow heads 228 and single or pluralextruders 235 may be used to flow resin to both flow heads.

Each mold 142 includes a parison knife mounted on the upstream side ofthe mold for severing the parisons 230 after the next or upstream moldhas closed on the parisons. This mold holds the parisons in alignmentfor capture by the next upstream mold. The parison knives areconventional and are not illustrated in the drawings.

Mold clamp assemblies 116 are mounted on the rotary sub-frame 102 ofmachine 100 at pivot support rods 208 and rotate continuously around theaxis of the main shift 104 during operation of the machine. At the sametime, the mold clamp assemblies rotate back and forth around pivot rods208 to shift the molds downstream and upstream on the rotating frame102. This shifting moves the molds 142 back and forth around rods 208through an angle of 22½° between lead or downstream positions andtrailing or upstream positions.

During operation of machine 100, rotary sub-frame 102 is rotated aroundthe axis of main shaft 104 at a constant speed in the direction of arrow232 shown in FIGS. 3 and 4. The circumferential position of a mold clampassembly on frame 102 is identified by the circumferential position ofthe pivot support rod 208 in the assembly starting at the 0° positionextending horizontally to the right of the main shaft as shown in FIG. 3and corresponding 90°, 180° and 270° positions and the return 360°position, as also illustrated in FIG. 3.

Frame 102 rotates each assembly 116 360° around main shaft 104. Followerroller 168 is moved into and along the groove in mold open and close cam120. This cam extends 115° around the main shaft from the 239° positionto the 354° position. The cam includes a radially inward 15° mold opensurface 234 located upstream of the 270° position and a 15° radialoutward mold close portion 236 located shortly before the 360° positionfor closing the molds on parisons 230.

With the mold halves 136, 138 in the open position and drive 182retracted as shown at the bottom of FIG. 2, rotation of shaft 104 movesthe open mold halves past extrusion station 113 to move rotary camfollower 168 along the slot in cam 120 and along radially outward moldclose surface 236. This movement rotates arm 156 to extend drive 182 andmove shift member 170 away from plate 148. Movement of the shift membermoves mold half 138 from the open position to the closed position.Movement of the shift member also actuates mold shift mechanism 200 tomove shift rod 180, rotate arm 186 and move mold half 136 from the openposition to the closed position. The connection between rod 194 andspring pack 198 is adjusted so that the spring pack is compressed whenthe mold is closed.

During and after closing of the mold, the clamp force exerted on moldhalf 136 is transmitted directly to drive 182 through mechanism 200. Anequal and oppositely directed clamp force is exerted on mold half 138and is transmitted to drive 182 directly through member 170. Clampingforces are not transmitted through rotary frame 102. The mold shiftmechanism floats on the mold clamp assembly and is not connected to therotary frame 102. As a result, frame 102 is not subjected to bendingmoments by the high clamp forces holding mold halves 136, 138 closed.The frame need not be strengthened against bending moments. Smaller,more efficient motors may be used to operate the machine. The molds areopened when rotation of the frame 102 moves follower roller 168 alongmold open surface 234 of cam 120.

Rotation of each mold clamp assembly about rod 208 and resultingupstream and downstream shifting of the mold are controlled by anassembly drive including upstream shift drive 117 and downstream shiftdrive 119. Upstream shift drive 117 includes cam 118 on the main frameand follower roller 212 on each mold clamp assembly and rotates theassemblies upstream on the rotating frame as the molds close on theparisons. Downstream shift drive 119 includes cam 122 on the main frameand followers 210 on the assemblies. The downstream shift drive 119rotates the mold assemblies about rods 208 in a downstream direction toposition the assemblies for upstream movement by drive 117.

Cam 118 extends 185° around the main shaft from the 337° position to the162° position and includes an inwardly extending downstream shift camsurface 238 extending 22½° around the main shaft for rotating the moldclamp assemblies 116 about rods 208 and shifting the molds in anupstream direction, counter to rotation of frame 102 as indicated byarrow 240 shown in FIG. 3. The remainder of cam 118 is circumferentialso that movement of follower rollers 212 through this portion of the camdoes not rotate the assemblies 116 or shift the molds.

Cam 122 extends slightly greater than 180° around the main shaft fromthe 155° position to the 340° position and includes a radially outwardextending cam surface 242 for rotating the mold clamp assemblies in thedirection of arrow 244, as shown in FIG. 3, to shift the mold in thedownstream direction. Surface 242 extends about 35° around the mainshaft at the 270° position. The remainder of cam 122 is circumferential.

As shown in Figs. 3 and 4, pivot rods 208 are located on frame 102radially inwardly from the molds. The downstream shift drive 119,advance cam 242 and followers 210 which engage cam 242 are locatedradially inwardly from the pivot rods 208. Drive 119, cam surface 242and follower rollers 210 are located radially inwardly of rods 208.

The upstream shift drive 117, retard cam 234 and followers 168 whichengage cam 234 are located radially outwardly of pivot rods 208 andradially inwardly from the mold halves 136. The downstream shift. drive119 is located radially inwardly from upstream shift drive 117 with rods208 between the two drives. The mold open and mold close cams 234, 236are located adjacent the mold halves in clamp assemblies 116, outwardlyfrom drives 117 and 119.

The cycle of operation of machine 100 will be explained by describingmovement of one mold clamp assembly 116 through a 360° revolution aroundshaft 104 starting with the pivot support rod 208 for the assembly atthe 320° position indicated by A in FIG. 3. In this position, followerroller 168 is in a circumferential portion of cam 120 and holds the moldhalves 136, 138 in the open position. Follower roller 210 is in acircumferential portion of cam 122 and holds the assembly with the moldin the circumferential advanced or downstream position on frame 102.Follower roller 212 is upstream from the entrance to cam 118.

Rotation of frame 102 moves the mold assembly counterclockwise as shownin FIG. 3 to position B where the open mold halves move freely to eitherside of flow heads 228, Continued rotation of the frame moves followerroller 212 into cam 118. Follower rollers 210 and 212 are incircumferential portions of their respective cams 122 and 118 andstabilize the assembly 116 during mold closing. Follower roller 168moves along mold close portion 236 of cam 120 to close the mold halveson upwardly extruded parisons 230 at position C. During closing of themold, the parisons are held in alignment, with. the flow heads and movevertically above the flow heads with the closed mold in the nextdownstream assembly 116. After the mold closes, roller 210 moves out ascam 122.

During movement of the assembly from position C to position D followerroller 212 moves along cam surface 238 to counter rotate the assembly116 upstream so that the mold is shifted upstream and slowed to thespeed of the parisons and the next downstream mold. The circumferentialspeed of the mold is reduced to less than the circumferential speed ofthe rotary frame and matches the extrusion rate for parisons 230.

The mold halves are fully closed on the parisons when in position C withthe cavities in alignment with the parisons and with the mold halvesmoving vertically upwardly above the flow heads with the parisons.During mold closing, the prior, downstream closed mold at position Dholds the parisons in alignment for capture as it moves verticallyupstream and its cam follower roller 212 moves along cam surface 238.

FIG. 3 illustrates that the mold in the assembly at position C closeswith the lead or downstream mold surface immediately adjacent thetrailing or upstream surface of the mold in the assembly at position Dand with the molds aligned and the mold cavities in axial alignment.This reduces flash extending between the molds. Both molds movevertically together above the flow heads. After the mold in the assemblyat position C is closed, the parison knife mounted on the downstream endof the closed mold at position D is actuated to sever the plasticextending between the two molds.

After the parisons extending between the two molds in the assemblies atpositions C and D are severed, continued rotation of the frame 102 movesfollower 212 on the assembly at position C along cam surface 238 torotate the assembly in the direction of arrow 240 to shift the closedmold in the assembly in the upstream direction and open a gap 226between the molds. The gap 226 between adjacent molds is maintaineduntil the mold assembly is rotated around to position O and follower 210moves along cam surface 242.

Gap 226 opens when the assembly is at position D. The blow pin unit 214on the mold in the assembly is then shifted by cylinder drive 137 fromthe retracted position shown in FIG. 5A to the inner work or blowposition over the closed mold halves, as illustrated in FIG. 5B. Theunit 214 engages plates 218. Retracted blow pins 220 are positioned overthe neck cavities 222 in the closed mold. The pressure cylinders 224 areactuated to extend the blow pins into the blow cavities andpressure-form the plastic in the cavities to provide finished necks.Blow gas is flowed into the parisons to blow mold the parisons againstthe cavities. The blow pin units are maintained on the molds in theposition shown in FIG. 6 during rotation of the mold clamp assembly 116from position D to position O. See FIG. 3. During this time, the blownparisons cool and set to form blow molded bottles with finished necks.

Movement of the assembly 116 from position O moves follower roller 168along mold open surface 234 to open the mold halves for ejection of theblown bottles at about the 270° position. Movement of cam followerroller 210 along cam advance surface 242 of cam 122 rotates the assembly116 in the direction of arrow 244 to shift the open mold downstream asthe assembly is returned to position A to complete a cycle of operation.

Partial circumferential cams 118 and 122 in the shift drives 117 and 119control the rotary position of the mold clamp assemblies on rods 208 asthe assemblies are rotated through cycles of operation. The ends of cams118 and 122 overlap to assure that one of the followers is moved intothe forward end of one cam before the other of the followers moves outof the trailing end of the other cam.

The molds 142 used in vertical rotary blow molding machine 100 blowcaptured parison segments by inserting blow pins in neck cavities. Ifdesired, machine 100 may be provided with molds having cavitiesincluding blow domes adjacent the neck portions of the bottle cavitiesand with blow needles for puncturing parison portions captured in theblow domes and flowing compressed gas into the captured portions toexpand the parisons against the cavities to blow mold bottles. Blow pinunits would not be provided. A machine with blow dome cavities and blowneedles would manufacture blow molded bottles as described with reducedflash and simplified extrusion equipment.

The parisons 230 are extruded upwardly at a speed which is less than thecircumferential speed of the mold due to the upstream rotation of themold. The cavities in the mold which close on the parisons move upstreamat the same speed as the molds move upstream during closing. This allowsthe next upstream mold to catch up with the previously closed mold sothat there is a minimum gap between the molds when the next upstreammold closes on the parisons and between-mold flash is reduced.

1. A continuous rotary blow molding machine including a main frame, amold close cam on the main frame; a rotary frame on the main frame; therotary frame having an axis of rotation; a motor for rotating the rotaryframe around the axis of rotation at a constant speed; a plurality ofmold clamp assemblies mounted on and spaced around the rotary frame,each mold clamp assembly including a blow mold having two opposed moldhalves movable toward and away from each other in a direction parallelto the axis of rotation, the mold halves defining a mold cavity when themold is closed, a mold close cam follower engaging the mold close cam,and a mechanical connection between the mold close cam follower and eachmold half whereby shifting of the mold close cam follower by the moldclose cam closes the mold; a flow head to extrude a first continuousparison downstream for capture by successive molds as the molds arerotated downstream and past the flow head; and an upstream mold-shiftmechanism for each mold clamp assembly, wherein each upstream mold-shiftmechanism shifts a mold in an upstream direction on the rotary frameafter the rotary frame rotates the mold in the assembly in a downstreamdirection over the parison and the mold actuation cam follower closesthe mold on the parison to position the closed mold adjacent to the nextupstream mold and reduce flash between the molds.
 2. The machine as inclaim 1 wherein each mold clamp assembly is rotatably mounted on therotary frame and each upstream mold-shift mechanism rotates a mold clampassembly upstream.
 3. The machine as in claim 2 including an upstreamshift cam on the main frame and wherein each mold clamp assemblyincludes a shift cam follower engaging the upstream shift cam.
 4. Themachine as in claim 2 wherein the upstream mold-shift mechanism rotateseach mold clamp assembly upstream about an axis parallel to the axis ofrotation.
 5. The machine as in claim 1 wherein each mold clamp assemblyincludes a base supporting a mold, and a rotary connection between thebase and the rotary frame for rotating the mold clamp assembly around anaxis parallel to the axis of rotation.
 6. The machine as in claim 1wherein said mold-shift mechanisms include an upstream shift cam on themain frame and a downstream shift cam on the main frame, and each moldclamp assembly includes two shift can followers with each cam followerengaging one shift cam.
 7. The machine as in claim 6 wherein the shiftcams are on opposite sides of the main frame.
 8. The machine as in claim1 including a downstream mold-shift mechanism.
 9. The machine as inclaim 1 wherein each mold has a second mold cavity, and including asecond flow head on the main frame spaced radially outwardly from thefirst flow head to extrude a second continuous parison downstream, and asingle extruder for flowing resin to both flow heads.
 10. The machine asin claim 9 including a single controller for both flow heads.
 11. Acontinuous rotary blow molding machine including a main frame, a moldactuation cam on the main frame, and an upstream shift cam on the mainframe; a rotary frame on the main frame; a drive for continuouslyrotating the rotary frame around an axis of rotation at a constantspeed; a plurality of mold clamp assemblies on and spaced around thecircumference of the rotary frame; a rotary connection between each moldclamp assembly and the rotary frame, each mold clamp assembly includinga blow mold, a mold actuation cam follower engaging the mold actuationcam, a mechanical connection between the actuation cam follower and theblow mold to open and close the blow mold, and an upstream shift camfollower engaging the shift cam; a first parison extruding flow head toextrude a parison for capture in cavities in molds rotated past the flowhead; wherein during downstream rotation of each open mold past the flowhead, the upstream shift cam moves the shift cam follower to rotate theassembly supporting such mold in an upstream direction so that the moldis moved adjacent to the next upstream mold when closed, whereinbetween-mold flash is reduced.
 12. The machine as in claim 11 includinga second parison extruding flow head, said first and second flow headslocated at different distances from the axis of rotation of the rotaryframe, each mold including radially spaced first and second moldcavities; and a single resin extruder for flowing resin to both saidflow heads.
 13. The machine as in claim 12 wherein the extrusion ratefor each parison equals the rate at which the molds move downstreamduring closing, wherein the molds move at the same speed as the parisonswhen closed.
 14. The machine as in claim 11 wherein each mold clampassembly includes a blow pin mounted on one mold half.
 15. The machineas in claim 14 wherein each mold clamp assembly includes a drive formoving the blow pin from a retracting position to a position in a gapbetween adjacent molds.
 16. The machine as in claim 1 wherein the flowhead extrudes the first parison upwardly.
 17. The machine as in claim 16wherein the axis of rotation is horizontal and the flow head extrudes avertical parison.
 18. The machine as in claim 1 wherein the flow headextrudes a parison at a speed less than the circumferential speed of therotary frame.
 19. The machine as in claim 1 including a rotaryconnection between each mold clamp assembly and the rotary frame, eachrotary connection located radially inwardly of the mold.
 20. The machineas in claim 19 wherein each mold clamp assembly includes a first camfollower engageable with a first cam on the main frame to rotate themold clamp assembly in the upstream direction after the rotary framemoves the mold in the assembly in a downstream direction over theparison and the mold close cam follower closes the mold on the parison.21. The machine as in claim 20 wherein the first cam is located radiallybetween the axis of rotation and the rotary connections.
 22. The machineas in claim 20 wherein each mold clamp assembly includes a second camfollower engageable with a second cam on the main frame, whereinmovement of the second cam follower in the second cam rotates the moldclamp assembly downstream when the mold clamp assembly is away from theflow head.
 23. The machine as in claim 22 wherein said first and secondcams are located radially inwardly from the molds.
 24. The machine as inclaim 23 wherein the flow head extrudes a parison at a speed less thanthe circumferential speed of the rotary frame at the molds.
 25. Themachine as in claim 24 including a second mold cavity in each mold,second flow head and a single extruder for flowing resin to each flowhead.
 26. The machine as in claim 25 including a single controller forboth flow heads.
 27. The machine as in claim 25 wherein the flow headsextrude parisons upwardly.
 28. The machine as in claim 27 wherein theaxis of rotation is horizontal, and the flow heads extrude verticalparisons.